Image forming apparatus with reduced posttransfer latent image

Abstract

An image forming apparatus includes a rotatable photosensitive drum including a photosensitive layer; a drum charging member contacted or disposed closely to the drum, to be supplied with a DC voltage; a developing device; a transfer member for transferring a toner image onto a toner image receiving member; a device for applying to the transfer member a transfer bias voltage; a light projecting portion for projecting light to the drum before the charging and after the image transfer; a controller for controlling a quantity of the projected light, on the basis of the transfer bias and a film thickness of the photosensitive layer, wherein under a condition that the transfer bias is the same, the light amount controlled by the controller is smaller when the film thickness is a fourth value than when it is a third value, the fourth value being smaller than the third value.

What is claimed is: 
     
       1. An image forming apparatus comprising:
 a rotatable photosensitive member including a photosensitive layer; 
 a charging member provided in contact with or in proximity with said photosensitive member and configured to be supplied with a DC voltage to charge a surface of said photosensitive member; 
 developing means configured to develop an electrostatic image formed on said photosensitive member into a toner image, after charging of said photosensitive member by said charging means; 
 a transfer member configured to transfer the toner image from said photosensitive member onto a toner image receiving member; 
 an application device configured to apply to said transfer member a transfer voltage for transferring the image from said photosensitive member onto the toner image receiving member; 
 a light projecting portion configured to project light to said photosensitive member before the charging by said charging means and after the image transfer by said transfer means; and 
 a controller configured to control a light quantity of the light projected to said photosensitive member by said light projecting portion, on the basis of information relating to the transfer voltage and information relating to a film thickness of said photosensitive layer, 
 wherein under a condition that the film thickness is the same, the light quantity controlled by said controller is smaller when the transfer voltage is a second value than when it is a first value, wherein a difference of the second value from a charged potential of said photosensitive member is smaller than that of the first value. 
 
     
     
       2. An apparatus according to  claim 1 , wherein under a condition that the transfer voltage is the same, the light amount controlled by said controller is smaller when the film thickness is a fourth value than when it is a third value, the fourth value being smaller than the third value. 
     
     
       3. An apparatus according to  claim 1 , wherein the information relating to the transfer voltage is a value of the transfer voltage or a value to be used for determining the transfer voltage. 
     
     
       4. An apparatus according to  claim 1 , wherein the information relating to the film thickness is one or a combination of two or more of a cumulative rotation time of said photosensitive member, a cumulative rotation number of said photosensitive member, a cumulative time of voltage application to said charging member, a current flowing through said charging member when a voltage is applied to said charging member, and cumulative contact time of a developing member of said developing means to said photosensitive member. 
     
     
       5. An apparatus according to  claim 1 , wherein said photosensitive member is provided in a cartridge mountable to a main assembly of said apparatus, and said cartridge is provided with storing means for storing the information relating to the film thickness. 
     
     
       6. An apparatus according to  claim 1 , wherein said transfer member is pressed toward and contact with said photosensitive member, a nip as a transferring portion is formed by said transfer member and said photosensitive member. 
     
     
       7. An apparatus according to  claim 1 , wherein said transfer member is a sponge roller including an electrically conductive metallic core and a foamed electrically conductive elastic layer. 
     
     
       8. An apparatus according to  claim 1 , wherein said controller is further configured to obtain information relating to the transfer voltage and to obtain information relating to the film thickness of said photosensitive layer, wherein said controller controls the light quantity of the light projected to said photosensitive member by said light projecting portion on the basis of the obtained information relating to the transfer voltage and the obtained information relating to a film thickness of said photosensitive layer.